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3 results on '"inner lipoyl domain"'

1. T cell responses to the putative dominant autoepitope in primary biliary cirrhosis (PBC).

Author

PALMER, DIAMOND, YEAMAN, BASSENDINE, JONES, and Bassendine, Margaret F.

Subjects
*T cells, *CIRRHOSIS of the liver, *PYRUVATES
Abstract

PBC is characterized by T cell-mediated destruction of the biliary epithelial cells lining the small intrahepatic bile ducts. The E2 and E3 binding protein (E3BP (protein X)) components of pyruvate dehydrogenase complex (PDC) are disease-specific autoantigens in PBC. Attempts to localize the T cell autoepitopes within PDC-E2 have, however, generated contradictory results. One study has suggested the presence of T cell epitopes throughout PDC-E2, whilst another has identified a single dominant 14 amino acid T cell epitope (p163) spanning the lipoic acid binding lysine residue in the inner lipoyl domain (ILD) of PDC-E2. The aim of the current study was to determine the prevalence of T cell responses to p163 and PDC-E2 ILD, and the role played by lipoylation of these antigens in their immunogenicity, in a UK PBC population. We found that the majority of the PBC patients showing a 6-day peripheral blood T cell proliferative response to native human PDC also responded, in a MHC class II-restricted fashion, to biochemically purified PDC-E2 and E3BP (which co-purify) (9/10 positive (SI > 2.76), mean SI 5.74 ± 5.04 (PDC-E2/E3BP) versus 6.67 ± 3.84 (PDC), P = NS), implying that the important PBC-specific T cell epitopes are contained within the PDC-E2 or E3BP components of PDC. Only a minority of patients responsive to PDC, however, responded to either lipoylated recombinant PDC-E2 ILD (4/10 positive, mean SI 1.98 ± 1.24, P < 0.005 versus PDC response) or lipoylated p163 (4/12 positive, mean SI 1.90 ± 1.58, P < 0.001). The lipoylation state did not affect the T cell response to either ILD or p163. Our findings suggest that in some UK patients with PBC there are immunodominant T cell autoepitopes within PDC-E2/E3BP which are outside the ILD of PDC-E2. [ABSTRACT FROM AUTHOR]

Published
1999
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2. The Fingerprint of Antimitochondrial Antibodies and the Etiology of Primary Biliary Cholangitis

Author

Shuai, Z, Wang, J, Badamagunta, M, Choi, J, Yang, G, Zhang, W, Kenny, T, Guggenheim, K, Kurth, M, Ansari, A, Voss, J, Coppel, R, Invernizzi, P, Leung, P, Gershwin, M, Shuai, Z, Wang, J, Badamagunta, M, Choi, J, Yang, G, Zhang, W, Kenny, T, Guggenheim, K, Kurth, M, Ansari, A, Voss, J, Coppel, R, Invernizzi, P, Leung, P, and Gershwin, M

Abstract

The identification of environmental factors that lead to loss of tolerance has been coined the Holy Grail of autoimmunity. Our work has focused on the reactivity of antimitochondrial autoantibodies (AMA) to chemical xenobiotics and has hypothesized that a modified peptide within PDC-E2, the major mitochondrial autoantigen, will have been immunologically recognized at the time of loss of tolerance. Herein we successfully applied intein technology to construct a PDC-E2 protein fragment containing amino acid residues 177-314 of PDC-E2 by joining a recombinant peptide spanning residues 177 to 252 (PDC-228) with a 62 residue synthetic peptide from 253 to 314 (PP), which encompasses PDC-E2 ILD. We named this intein-constructed fragment PPL. Importantly, PPL, as well as lipoic acid conjugated PPL (LA-PPL) and xenobiotic 2-octynoic acid conjugated PPL (2OA-PPL), are recognized by AMA. Of great importance, AMA has specificity for the 2OA modified PDC-E2 ILD peptide backbone distinct from antibodies that react with native lipoylated PDC-E2 peptide. Interestingly, this unique AMA subfraction is of the IgM isotype and more dominant in early stage PBC, suggesting that exposure to 2OA-PPL-like compounds occurs early in the generation of AMA. To understand the structural basis of this differential recognition we analyzed PPL, LA-PPL and 2OA-PPL using electron paramagnetic resonance spectroscopy, with confirmations by ELISA, immunoblotting and affinity antibody analysis. We demonstrate that the conformation of PDC-E2 ILD is altered when conjugated with 2OA, compared to conjugation with lipoic acid. In conclusion a molecular understanding of the conformation of xenobiotic modified PDC-E2 is critical for understanding xenobiotic modification and loss of tolerance in PBC with widespread implications for a role of environmental chemicals in the induction of autoimmunity. This article is protected by copyright. All rights reserved

Published
2017

3. The Fingerprint of Antimitochondrial Antibodies and the Etiology of Primary Biliary Cholangitis

Author

Madhu Badamagunta, Weici Zhang, Jinjun Wang, Pietro Invernizzi, Jinjung Choi, Patrick S.C. Leung, Guo-Xiang Yang, Aftab A. Ansari, Kathryn G. Guggenheim, Zongwen Shuai, John C. Voss, Mark J. Kurth, M. Eric Gershwin, Thomas P. Kenny, Ross L. Coppel, Shuai, Z, Wang, J, Badamagunta, M, Choi, J, Yang, G, Zhang, W, Kenny, T, Guggenheim, K, Kurth, M, Ansari, A, Voss, J, Coppel, R, Invernizzi, P, Leung, P, and Gershwin, M

Subjects
0301 basic medicine, Cholangitis, inner lipoyl domain, intein mediated ligation, Clinical Sciences, Immunology, Antibody Affinity, Peptide, Enzyme-Linked Immunosorbent Assay, Medical Biochemistry and Metabolomics, medicine.disease_cause, Autoimmune Disease, Article, primary biliary cholangiti, Autoimmunity, Xenobiotics, Inteins, 03 medical and health sciences, chemistry.chemical_compound, Rare Diseases, E2 subunit of the pyruvate dehydrogenase, MED/12 - GASTROENTEROLOGIA, medicine, Humans, Pyruvate Dehydrogenase (Lipoamide), xenobiotics, Autoantibodies, 2-octynoic acid, chemistry.chemical_classification, Hepatology, biology, Gastroenterology & Hepatology, Autoantibody, Electron Spin Resonance Spectroscopy, electron paramagnetic resonance spectroscopy, hemic and immune systems, Isotype, Mitochondria, Lipoic acid, 030104 developmental biology, chemistry, Biochemistry, Antimitochondrial antibodie, Case-Control Studies, biology.protein, Protein Fragment, Antibody, Intein
Abstract

The identification of environmental factors that lead to loss of tolerance has been coined the holy grail of autoimmunity. Our work has focused on the reactivity of antimitochondrial autoantibodies (AMA) to chemical xenobiotics and has hypothesized that a modified peptide within PDC-E2, the major mitochondrial autoantigen, will have been immunologically recognized at the time of loss of tolerance. Herein, we successfully applied intein technology to construct a PDC-E2 protein fragment containing amino acid residues 177-314 of PDC-E2 by joining a recombinant peptide spanning residues 177-252 (PDC-228) with a 62-residue synthetic peptide from 253 to 314 (PP), which encompasses PDC-E2 inner lipoyl domain (ILD). We named this intein-constructed fragment PPL. Importantly, PPL, as well as lipoic acid conjugated PPL (LA-PPL) and xenobiotic 2-octynoic acid conjugated PPL (2OA-PPL), are recognized by AMA. Of great importance, AMA has specificity for the 2OA-modified PDC-E2 ILD peptide backbone distinct from antibodies that react with native lipoylated PDC-E2 peptide. Interestingly, this unique AMA subfraction is of the immunoglobulin M isotype and more dominant in early-stage primary biliary cholangitis (PBC), suggesting that exposure to 2OA-PPL-like compounds occurs early in the generation of AMA. To understand the structural basis of this differential recognition, we analyzed PPL, LA-PPL, and 2OA-PPL using electron paramagnetic resonance spectroscopy, with confirmations by enzyme-linked immunosorbent assay, immunoblotting, and affinity antibody analysis. We demonstrate that the conformation of PDC-E2 ILD is altered when conjugated with 2OA, compared to conjugation with lipoic acid. Conclusion: A molecular understanding of the conformation of xenobiotic-modified PDC-E2 is critical for understanding xenobiotic modification and loss of tolerance in PBC with widespread implications for a role of environmental chemicals in the induction of autoimmunity. (Hepatology 2017;65:1670-1682).

Published
2017

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